US3745261A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Telephone set speech network
Assignee: AT&T Inc
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Filing: 1971-09-20
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Granted: 1973-07-10
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Expires: 1991-09-20
Abstract
Abstract In an electronic type telephone set employing an active resistive hybrid network in combination with separate transmit and receive feedback amplifiers, automatic equalization in terms of both frequency and volume is achieved by the use of a respective photoresistive device in each of the amplifier feedback paths. Each of the photoresistive devices is optically coupled to a common light-emitting diode in a line current sensing circuit that forms an integral part of the active resistive hybrid network.
Inventors
- 👤 S Friedman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:32
CPC Classifications
H; H04; H04M; H04M1/00; H04M1/738; H04M1/76; H04M1/58; H04M1/585
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
126 words
A speech network for a telephone set comprising, in combination, a transmit path including a transmitter and a transmit equalizer-amplifier having a feedback loop with an equalizer network connected therein, a receive path including a receiver and a receive equalizeramplifier having a feedback loop with an equalizer network therein, and an active resistive hybrid network including a line currentsensing circuit, said hybrid connecting said transmit and receive paths to common line terminals, said sensing circuit including means responsive to the level of said line current for generating light without additional voltage loss in said set, and each of said equalizer networks including a respective photoresistive device optically coupled to said light generating means, whereby said equalizer networks control both frequency and amplitude equalization in said paths.
Claim 2
Dependent Claim
126 words
A speech network for a telephone set comprising, in combination, a transmit path including a transmitter and a transmit equalizer-amplifier having a feedback loop with an equalizer network connected therein, a receive path including a receiver and a receive equalizeramplifier having a feedback loop with an equalizer network therein, and an active resistive hybrid network including a line currentsensing circuit, said hybrid connecting said transmit and receive paths to common line terminals, said sensing circuit including means responsive to the level of said line current for generating light without additional voltage loss in said set, and each of said equalizer networks including a respective photoresistive device optically coupled to said light generating means, whereby said equalizer networks control both frequency and amplitude equalization in said paths.
Claim 3
Dependent Claim
15 words
Apparatus in accordance with claim 1 wherein said light generating means comprises a light-emitting diode.
Claim 4
Dependent Claim
66 words
Apparatus in accordance with claim 2 wherein said sensing circuit includes a conducting path between said line terminals, said path including the series connected combination of said light-emitting diode, the collector-emitter path of a current controlling transistor and a resistive device, said light-emitting diode being connected in the collector circuit of said transistor and said resistive device being connected in the emitter circuit of said transistor.
Claim 5
Dependent Claim
23 words
Apparatus in accordance with claim 3 wherein a biasing diode is connected between the base electrode of said transistor and a reference potential.
Claim 6
Dependent Claim
22 words
Apparatus in accordance with claim 4 further including a biasing resistor connected between said base electrode and a source of biasing potential.
Claim 7
Dependent Claim
29 words
Apparatus in accordance with claim 2 including resistive means shunting said light-emitting diode thereby effectively increasing the slope of the I vs. R characteristic curves of said photoresistive devices.
Claim 8
Dependent Claim
43 words
Apparatus in accordance with claim 2 wherein each of said equalizer networks comprises, respectively, a resistive device in series relation with said photoresistive device and a capacitive device connected between the common terminal of said last two named devices and a reference potential.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-09 | 1977-01-08 | 1977-07-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-09 | 1981-01-08 | 1981-07-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-09 | 1985-01-08 | 1985-07-10 | $7700.00 | Window Closed / Lapsed |